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package ee.tlu.htk.dippler.course;

import ee.tlu.htk.dippler.backoffice.StatusCodes;
import ee.tlu.htk.dippler.entities.Course;
import ee.tlu.htk.dippler.entities.Grade;
import ee.tlu.htk.dippler.entities.Learner;
import ee.tlu.htk.dippler.entities.User;
import ee.tlu.htk.dippler.utils.permissionChecker;
import java.io.StringReader;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.ejb.EJB;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;

/**
 *
 * @author pjotr
 */
@Stateless
public class GradeManager implements GradeManagerLocal {
    @PersistenceContext
    private EntityManager em;
    @EJB private CourseManagerLocal courseManager;
    @EJB private LearnerManagerLocal learnerManager;
    
    private Unmarshaller unmarshaller = null;
    
    public GradeManager() {
        try {
            final JAXBContext context = JAXBContext.newInstance(Grade.class);
            unmarshaller = context.createUnmarshaller();
        } catch (JAXBException ex) {
            Logger.getLogger(GradeManager.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    
    
    @Override
    public String saveGrade(String data, User user) {
        Grade new_grade = unMarshal(data);
        if (new_grade != null) {
            Learner learner = learnerManager.findById(new_grade.getId());
            if (learner != null) {
                Course course = courseManager.findById(learner.getCourse().getId());
                if (!permissionChecker.isFacilitator(user, course)) {
                    return StatusCodes.respond(StatusCodes.OPERATION_NOT_ALLOWED, "Not facilitator or admin");
                }
                Grade grade = findById(new_grade.getId());
                Date date = new Date();
                if (grade != null) { 
                    grade.setModified(date);
                    grade.setGrade(new_grade.getGrade());
                    grade.setFeedback(new_grade.getFeedback());
                } else {
                    new_grade.setCreated(date);
                    new_grade.setModified(date);
                    new_grade.setLearner(learner);
                    learner.setGrade(new_grade);
                }
                return StatusCodes.respond(StatusCodes.SUCCESS, "");
            }
        }
        return StatusCodes.respond(StatusCodes.COURSE_ERROR, "Save grade failed");
    }
    
    @Override
    public String loadGrade(String data, User user) {
        Grade grade = findByData(data);
        if ( grade != null ) {
            Course course = courseManager.findById(grade.getLearner().getCourse().getId());
            if (!(permissionChecker.isFacilitator(user, course) || permissionChecker.isOwner(user, grade.getLearner().getUser()))) {
                return StatusCodes.respond(StatusCodes.OPERATION_NOT_ALLOWED, "Not facilitator or admin");
            }
            return StatusCodes.respondWithData(StatusCodes.SUCCESS, "", marshal(grade));
        }
        return StatusCodes.respond(StatusCodes.COURSE_ERROR, "Not loaded");
    }
    
    public Grade unMarshal(String data) {
        if ( unmarshaller != null ) {
            try {
                final Grade gradeUNM = (Grade) unmarshaller.unmarshal(new StringReader(data));
                return gradeUNM;
            } catch(JAXBException e) {
                //something went wrong
            }
        }
        return null;
    }
    
    @Override
    public String marshal(Grade grade) {   
        StringBuilder xml = new StringBuilder("<grade>");
        xml.append("<id>").append(grade.getId().toString()).append("</id>");
        xml.append("<learner_id>").append(grade.getLearner().getId().toString()).append("</learner_id>");
        xml.append("<user_id>").append(grade.getLearner().getUser().getId().toString()).append("</user_id>");
        xml.append("<course_id>").append(grade.getLearner().getCourse().getId()).append("</course_id>");
        xml.append("<grade><![CDATA[").append(grade.getGrade()).append("]]></grade>");
        xml.append("<feedback><![CDATA[").append(grade.getFeedback()).append("]]></feedback>");
        xml.append("<created>").append(grade.getCreated()).append("</created>");
        xml.append("<modified>").append(grade.getModified()).append("</modified>");
        xml.append("</grade>");
        return xml.toString();
    }
    
    public Grade findByLearnerId(Long id) {
        if ( id != null && id > 0 ) {
            return em.find(Grade.class, id);
        }
        return null;
    }
    
    public Grade findById(Long id) {
        return findByLearnerId(id);
    }
    
    public Grade findByUserAndCourseIds(Long user_id, Long course_id) {
        if ( user_id > 0  && course_id > 0) {
            Query find = em.createNamedQuery("Grde.findByUserAndCourseIds");
            find.setParameter("user_id", user_id);
            find.setParameter("course_id", course_id);
            try {
                Grade grade = (Grade) find.getSingleResult();
                return grade;
            } catch(Exception e) {
                //Could not find profile
            }
        }
        return null;
    }
    
    public Grade findByData(String data) {
        Grade fake_grade = unMarshal(data);
        if (fake_grade.getId() != null && fake_grade.getId() > 0) {
            return findById(fake_grade.getId());
        } else if (fake_grade.user_id != null && fake_grade.user_id > 0 && fake_grade.course_id != null && fake_grade.course_id > 0) {
            return findByUserAndCourseIds(fake_grade.user_id, fake_grade.course_id);
        }
        return null;
    }

}